undercover
1. [ adjective ] conducted with or marked by hidden aims or methods
Synonyms: secret clandestine surreptitious hush-hush hugger-mugger on_the_quiet hole-and-corner underground cloak-and-dagger
Examples:

"clandestine intelligence operations" "cloak-and-dagger activities" "secret missions" "surreptitious mobilization of troops" "an undercover investigation" "underground resistance"

Related terms: covert
Similar spelling:   underperform
  undercoat
  undertaker
  underscore
  underwater
  underquote
  undergo
  undervalue
  undercharge
  undercoated
  underage
  underlie
  undercut
  underfur
  underwriter
  underactive
  undercurrent
  underseller
  underlay
  under_control
  underived
  undergrow
  undermine
  underdone
  underfoot
  underfed
  underdrawers
  underdog
  undercarriage
  underbid
  underarm
  underact
  under_it
  undergird
  underpart
  underline
  underpay
  underwood
  underwear
  underway
  undertow
  undertone
  undertide
  undertake
  undersurface
  underside
  undershot
  undersize
  underpin
  underproduce
  underrate
  undersea
  undergrad
  underworld
  under_way
  underwing
  underling
  underplay
  underbody
  underboss
  underbred
  underclass
  underseal
  underivative
  understood
  understock
  Underdahl
  undersoil
  underpass
  Underdown
  undersign
  Underhill
  underfelt
  undershrub
  underhand
  undershoot
  undersell
  underhung
  under_arms